Typical visible index systems of the removable pocket card type are shown by way of example in U.S. Pat. No. 1,811,245 to Powell and U.S. Pat. No. 2,217,018 to Hopkins. In such systems a plurality of overlapping pocket card holders are supported by hinges from wire hangers carried in suitable frames. The frames are provided with spaced parallel flanges or turn-overs at the opposite sides thereof. The cards are hinged upon the wire hangers by means of hinges formed of metal which are fastened to the card.
Each hanger comprises a length of resilient wire having a straight main body portion with return ends bent to form a return portion which extends inwardly towards the main body portion for a limited distance. The bent end returns are axially offset relative to the axis of the main body of the hanger and terminate in off-set bent ends which lie adjacent and axially parallel to the main body portion. The hinges are mounted for pivotal movement on these ends.
The entire hanger lies substantially in a single plane which includes the main body portion, the returns, the off-set bent portions and the ends which lie adjacent and parallel to the main body portion. As seen from a top or plan view the hangers are asymmetrical with loops lying on one side of the axis of the main body portion. The hinge mounted pocket card holders may be easily removed from the tray without removing the hanger. However it is also desired that the hangers be readily insertable and removable to facilitate deletion or addition of cards and particularly to permit shifting of cards as for example to keep the cards is alphabetic or other order.
While pocket card mounting arrangements of the type illustrated in the Powell and Hopkins patents are generally acceptable and are in widespread commercial use they suffer from certain disadvantages. One such disadvantage is that the wire hanger is subject to insertion in the frame side channels or turn-overs in either of two positions. In the correct position the ends of the hanger lie above the main body and the hinges depend from these upper end portions of the hanger.
However, it is also possible to mount the wire hanger in the frame or tray in the opposite disposition wherein the hanger ends are disposed beneath the main body of the hanger. The hinges may be mounted on the hanger ends just as readily as in the former instance and the pocket card holder will pivot on the hanger. However, the main body and hinge axis spacing between adjacent hangers becomes random and varied with the result that irregular index spaces are provided. This tends to create index visibility problems. Because the index system is intended to be used and is used by a large number of persons who may not have frequent need of removing and inserting hangers it is relatively easy for hangers to be inserted in the undesired disposition thereby creating the undesired and troublesome mounting arrangement described above.
Other configurations of wire hangers of this general type are also disclosed in prior patents. Examples of illustrative variations are found in U.S. Pat. No. 1,153,520 to Rosenberger, U.S. Pat. No. 1,360,574 to Phillips, U.S. Pat. No. 1,574,893 to Hutchings, U.S. Pat. Nos. 2,298,290 and 2,246,584 to Hall and German Patent No. 458,524 to Blodner. The hanger constructions illustrated in these patents are generally asymmetrical and result in arrangements which do not preclude erroneous hanger insertion.